Light weight sabot

ABSTRACT

A sabot having a plurality of substantially hollow, J-shaped petals. Integrally formed support struts extend radially inward from the petal surface to engage positioning grooves in the projectile skin. Driving band sections are swaged into recesses formed in the petals and a pre-notched holding band secures the petals to the projectile. The J-shaped curved portion engages an aft-positioned circumferential groove to transmit driving forces to the projectile.

. a v States Kornblith et a1.

LIGHT WEIGHT SABOT Inventors: Jeffrey S. Kornblith, Oxon Hill.

Md.; Jerold 1L. Swedlow, Pittsburgh, Pa.

The United States of America as represented by the Secretary of theNavy, Washington, DC.

Filed: 1 Nov. 21, 1972 Appl. Nd; 308,382

Assignee:

US. Cl 102/93, 102/56, 102/926 Int. Cl. F42b 13/16, F42b 31/00 Field ofSearch 102/52, 93, 94, 56, 92.6,

' References Cited FOREIGN PATENTS OR APPLICATIONS 1,231,601 4/1960France 102/93 1 .lan.28, 1975 1,016,766 9/1952 France 102/93 PrimaryExaminer-Robert F. Stahl Attorney, Agent, or Firm-R. S. Sciascia; J. A.Cooke [57] ABSTRACT A sabot having a .plurality of substantially hollow,J- shaped petals. integrally formed support struts extend radiallyinward from the petal surface to engage positioning grooves in theprojectile skin. Driving band sections are swaged into recesses formedin the petals and a pre-notched holding band secures the petals to theprojectile. The .l-shaped curved portion engages an aft-positionedcircumferential groove to transmit driving forces to the projectile.

19 Claims, 4 Drawing Figures FATE FEB MM 2 81975 I LIGHT WEIGHT SABOTBACKGROUND OF THE INVENTION port. With fin stabilized projectiles, asingle sabot positioned near the center of gravity is usually employedwith the fins designed to ride the bore of the launcher and provide thesecond support point.

Currently used sabots are generally solid or nearly solid pieces made ofmaterial such as steel or aluminum. The petals of these sabots areoverly heavy and travel appreciable distances after separation from theprojectile. Heavy sabot petals decrease the range of the projectile andpresent a serious hazard to personnel and property in the launch area asthey fall afterseparation. During assembly, each petal must be securelyattached, such as with a plurality of fastening keys, necessitatingadditional steps in assembly and requiring more parts in the sabot.

SUMMARY OF THE INVENTION Accordingly, one object of this invention is toprovide a new and improved sabot device for subcaliber projectiles.

Another object of the invention is to provide a new and improved sabotthat is light in weight and structurally adequate to sustain the imposedloads.

Another object of the invention is to provide a new and improved lightweight sabot having fewer parts than sabot designs heretofore used.

Still another object of the present invention is the provision of alight weight sabot with improved locking mechanism.

Yet still another object of the instant invention is to provide animproved sabot device with petals presenting minimum hazard upondiscard.

Briefly, in accordance with one embodiment of this invention, these andother objects are attained by providing a sabot device having aplurality of identical, light weight petals secured to the subcaliberprojectile with a pre-notched holding band. Each petal comprises acurved outer surface with an inwardly curved aft portion and havingintegrally formed struts extending radially inwardly from the surface toengage grooves formed in the projectile. Swagged into recesses formed inthe petal outer surfaces are sections of a driving band which engagesthe barrel of the launch device. When positioned upon the projectile,the sabot device forms a substantially concentric, truncated cylinderwith the curved aft portion engaging a circumferential groove formed inthe end of the projectile and the struts positioning and supporting theprojectile within the launcher barrel.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of theinvention and many of the attendant advantages thereof will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein: I

FIG. 1 is a side view of a projectile embodying the sabot of the presentinvention; 7

FIG. 2 is a side elevational view of the sabot of FIG. I partly insection and to an enlarged scale;

FIG. 3 is a cross-sectional view of the sabot taken along line 3-3 ofFIG. 2 with one sabot petal displaced for greater clarity; and

FIG. 4 shows a perspective view of a petal of the sabot.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,wherein like reference characters designate identical or correspondingparts throughout the several views, and more particularly to FIG. 1thereof, subcaliber projectile 10 is shown supported in the rifledbarrel 12 of a suitable launch device. While projectile 10 is shown tobe of the spin-stabilized type, it is understood that the sabot of thepresent invention may be equally advantageously used with tin-stabilizedprojectiles and smooth bore launch devices. Projectile 10 is supportedapproximate the front end by front riders 14 of the type known and usedin the art and the aft tail portion of the projectile is positioned andsupported by the sabot device of the present invention, generallydesignated as 18. A triangular wedge ring 16 is positioned on theprojectile forward of the sabot to facilitate loading into the barrel,as will be more fully described hereinafter. An obturator 20, also ofthe type known and used in the art, is positioned aft of sabot 18 andprovides a fluid seal for the propellant gas and transmits the drivingforce to the sabot and projectile.

Referring now to FIGS. 2 and 3., sabot 18 comprises a plurality ofidentical, substantially hollow segments or petals 24., four such petalsbeing shown only for purposes of illustration. A lesser or larger numberof petals may be used, with corresponding changes in the num' ber ofreceiving grooves formed in the projectile skin. A recess 26 is providedat the forward end of petal 24 to receive a holding band 34 which isdescribed more fully hereinbelow. Recess 28, positioned behind and ofgreater depth than holding band recess 26, occupies a substantialportion of petal exterior surface 22 and receives driving band section32, described more fully below. Pyramidal-shaped protrusions 40,integrally formed on the base of driving band recess 28, will penetratethe inner surface of the copper driving band section 32 which is swaggedinto recess 28 to ensure a tight, non-slipping attachment with petal 24.Obviously, other shapes for protrusions 40 are within the scope of theinvention.

The aft end portion 30 of sabot petal 24 terminates in an arcuatefashion, curving inwardly and then extending towards the forward endportion such that, when viewed in the longitudinal side section of FIG.2, petal 24 has substantially a Lshape. The arcuate portion 30 of the Jis thickened to sustain the axial driving forces transmitted to sabot 18via obturator 20. Curved portion 30 terminates at lip 36 which engages acoupling groove 38 circumferentially formed in the aft end of projectile10. Lip 36 cooperates with groove 38 to 7 both position the sabot and totransmit to the projectile mate the aft end thereof. The cooperativerelationship between struts 42, 44 and grooves 46, 48 serves to positionthe petal 24 circumferentially on projectile l and provides themechanical linkage between the barrel wall 12'of the launching deviceand the projectile. Side or positioning struts 42 are integrally formedat the longitudinal edges of petal 24. Struts 42 taper radially inwardlyand terminate in half-V-shaped end or foot portions 50 which fitmatingly with similarly configured V- shaped grooves 46 to positionsegments'24 onto the projectile. As shown in FIG. 3, each side struts 42has a longitudinally extending, flush, flat surface 56 which abutindentical surfaces of adjacently positioned segments and extendsradially inward from outer surface 22 to provide unencumbered surfacesof separation of the sabotpetals after projectile launch.

Thecenter strut 44 of each petal 24 also is integrally formed with petalsurface 22 and extends radially inwardly, terminating in a squared-off,flat foot portion 52 which matingly engages similarly configured centerstrut groove 48 formed on the projectile skin. Center strut 44 isinclined relative to the radial direction at an angle determined by thetorsional loads imposed upon shown in FIG. 4. In using the sabot of thepresent invention in non-spin stabilized projectiles, the center strutneed not necessarily be inclined since torsional loads are notencountered and may be omitted completely if so desired.

While the preferred embodiment described hereinabove shows each sabotpetal to have two side struts and an inclined center strut, it is Withinthe purview of the invention that the number of struts may be other thanas shown. For example, additional center struts may be provided ifnecessitated by load requirements or similarly the center strut may beeliminated all together. Alternatively, all the struts, i.e., the sideas well as the center struts, may be angularly inclined.

As set forth hereinabove, the aft portion of the projectile is providedwith a plurality of longitudinal grooves 46, 48 and circumferentialgroove 38, preferrably machined into the skin of the projectile. Thelength of the longitudinal grooves should be at least as long as thesabot but may be longer. Groove 38 extends completely around the aft endof projectile 10.

Sabot petals 24, with integrally formed struts 42, 44 and .l-shapecurved end portion 30, may be fabricated by any suitable method, forexample, such as casting or machining. Investment casting presentsadvantages in producting intricate shapes with minimum manual finishingrequired. Any suitable material may be used in fabricating the sabot,such as aluminum or steel or any alloy capable of withstanding theapplied stresses. Aluminum is desirable since it is light in weight andstrong.

The driving band sections 32, of any suitable material, such as copper,are swaged onto each petal prior to assembly of sabot 18 onto theprojectile. The swagg ing process forces the band sections 32 into thedriving band recess 28, causing portrusions 40 to penetrate the innersurface of sections 32 and to become embedded therein, resulting in atight, non-slipping attachment of band section 32. In the preferredembodiment the outer surface of section 32 is smooth, i.e., the surfaceis not pre-engraved with grooves which engage the barrel riflings. Thispermits ready use of sabot 18 in both smooth and rifled barrels. Thesmooth surface of section 32, upon loading of the projectile, engagesthe barrel riflings and becomes engraved during launch. However, section32 may be pre-engraved with rifling grooves. During launch, the drivingband engages the rifling of barrel l2, imparting rotation to projectile10 as the projectile proceeds within the barrel.

The holding band 34, which may be made of any suitable material, such asbrass, is adapted to be positioned within recess 26, the free endsthereof being suitably secured, as by spot welding. Band 34 may beprovided with a plurality of notches, spaced along its length, to permitthe band to fracture at these notch points.

Wedge ring 16, of substantially triangular cross section and made of anysuitable material, such as plastic, in an annular device which ispositioned upon projectile 10 forward of grooves 46, 48 before petals 24are attached'The inner diameter of ring 16 is sized to achieve thisposition. Forward surface 62 of ring 16 is inclined relative to thesurface of the projectile with aft surface 64 flat to abut the forwardedge surface of sabot 18. The primary objective of ring 16 is tofacilitate loading of projectile 10. Subsequent to launch, ring 16slides off the tapered aft portion of the projectile after petals 24have separated. Alternatively, ring 16 may be provided with a pluralityof notches or otherwise structurally weakened to cause structuralfailure of the ring, permitting ring 16 to separate in pieces undercentrifugal spinning forces.

Fitted obturator 20, fabricated of any suitable material, such asplastic, is positioned aft of sabot I8 behind projectile 10. The aftsurface 58 of obturator 20 is sub- I stantially flat, presenting a flatsurface against which the propellant gas expands, while the forwardsurface 60 is contoured to conform to the curvature of the aft end ofsabot 18. As shown in FIG. 2, obturator 20 may be flared outwardly, formthe forward surface 60 toward the aft surface 58 to ensure a tight gasseal between the obturator and barrel 12.

Prior to loading the projectile into the launch device, sabot 18 andfront riders 14 are assembled onto projectile 10. The front riders arepositioned and attached to projectile 10 by suitable, well-known means,such as fitting grooves, securing bands or straps, or separate stabilizeit. After exiting from the barrel. the obturator present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. A sabot comprising a plurality of separable seg-' ments andrupturable means to secure said segments in assembled condition, each ofsaid segments having arcuate, longitudinally extending inner and outersurfaces, one longitudinal end terminating in a portion curved towardsaid inner surface to form a substantially J-shape when viewed inlongitudinal section, said arcuate surfaces being curved in thedirection transverse to the longitudinal direction, and a plurality oflongitudinal support struts integrally formed with and extending thelongitudinal length of said inner surface.

2. The sabot of claim 1 wherein a first set of select ones of saidlongitudinal struts are angularly inclined with respect toperpendiculars to said curved surfaces.

3. The sabot of claim 2 wherein a second set of select ones of saidstruts comprise planar surfaces of separation permitting said arcuatesurface to separate into a plurality of segments.

4. The sabot of claim 3 wherein said rupturable securing means comprisesa band receivable in a recess in said surface.

5. The sabot of claim 4 further comprising force transmission meanspositioned on said surface.

6. The sabot of claim 5 wherein said force transmission means comprisedriving band sections positioned in a second recess in said surface.

7. A sabot device for projectiles comprising:

a plurality of separable petal segments, each of said segments having:

arcuate, longitudinally extending inner and outer surfaces, saidsurfaces being curved in the direction transverse to the longitudinaldirection, one longitudinal end portion curved toward said inner surfaceto form a J-shape to be received within the aft end portion of theprojectile, and a plurality of longitudinal support struts integrallyformed with and extending the longitudinal length of said inner surfaceto support said petal segment on the projectile;

rupturable securing means positioned on said petal segments to hold saidsegments in assembled condition on the projectile; and

force-transmitting drive means positioned on said petal segments totransmit the driving force to the projectile.

8. The sabot device of claim 7 wherein at least one of said longitudinalstruts is inclined with respect to said arcuate outer surface.

9. The sabot device to claim 7 wherein at least two of said longitudinalstruts are integrally formed along the lateral edges of said petalsegment forming a flat surface whereby the flat surfaces of abuttingpetal segments form planes of separation.

10. The sabot device of claim 9 further comprising an additionallongitudinal strut positioned between said lateral edge struts andinclined with respect to a perpendicular to said arcuate outer surface.

11. The sabot device of claim 10 wherein said drive means comprise aplurality of driving band sections positioned within a recess in saidpetal segments.

12. The sabot device of claim 11 wherein said securing means comprise aholding band positioned in a second recess in said petal segmentsadapted to rupture under centrifugal force.

13. The sabot device of claim 12 further comprising an annular wedgering positioned on the projectile forwardly of said petal segments and acontoured obturator abutting said inwardly curved end portion of saidpetal segments.

14. In combination, a projectile having a plurality of longitudinallyextending grooves circumferentially spaced on the exterior, aft surfaceand a sabot device comprising:

a plurality of separable petal segments, each segment having arcuate,longitudinally extending inner and outer surfaces with aninwardly-curved, J-shape'd, longitudinal end portion, and

a plurality of longitudinal support struts integrally formed with andextending the longitudinal length of said inner surface to engage saidlongitudinal grooves;

projectile drive means positioned on said petal seg ments; and

rupturable securing means receivable on said petal segments to hold saidsegments in assembled condition on said projectile.

15. The combination of claim 14 further comprising a circumferentialgroove formed in the aft end portion of said projectile to receive saidinwardly curved, J- shaped end portion of said petal segments.

16. The combination of claim 15 wherein at least one of saidlongitudinal struts is inclined with respect to the radial direction ofsaid arcuate surfaces.

17. The combination of claim 16 wherein said projec' tile drive meanscomprise sections of a driving band positioned within a recess in saidpetal segments and said rupturable securing means comprise a notchedholding band.

18. The combination of claim 17 further comprising:

an annular wedge ring positioned on said projectile forwardly of saidpetal segments and an obturator positioned aft of said projectileabutting said petal segments.

19. The combination of claim 14 further comprising:

an annular wedge ring positioned on said projectile forwardly of saidpetal segments and an obturator positioned aft of said projectileabutting said petal segments.

1. A sabot comprising a plurality of separable segments and rupturablemeans to secure said segments in assembled cOndition, each of saidsegments having arcuate, longitudinally extending inner and outersurfaces, one longitudinal end terminating in a portion curved towardsaid inner surface to form a substantially J-shape when viewed inlongitudinal section, said arcuate surfaces being curved in thedirection transverse to the longitudinal direction, and a plurality oflongitudinal support struts integrally formed with and extending thelongitudinal length of said inner surface.
 2. The sabot of claim 1wherein a first set of select ones of said longitudinal struts areangularly inclined with respect to perpendiculars to said curvedsurfaces.
 3. The sabot of claim 2 wherein a second set of select ones ofsaid struts comprise planar surfaces of separation permitting saidarcuate surface to separate into a plurality of segments.
 4. The sabotof claim 3 wherein said rupturable securing means comprises a bandreceivable in a recess in said surface.
 5. The sabot of claim 4 furthercomprising force transmission means positioned on said surface.
 6. Thesabot of claim 5 wherein said force transmission means comprise drivingband sections positioned in a second recess in said surface.
 7. A sabotdevice for projectiles comprising: a plurality of separable petalsegments, each of said segments having: arcuate, longitudinallyextending inner and outer surfaces, said surfaces being curved in thedirection transverse to the longitudinal direction, one longitudinal endportion curved toward said inner surface to form a J-shape to bereceived within the aft end portion of the projectile, and a pluralityof longitudinal support struts integrally formed with and extending thelongitudinal length of said inner surface to support said petal segmenton the projectile; rupturable securing means positioned on said petalsegments to hold said segments in assembled condition on the projectile;and force-transmitting drive means positioned on said petal segments totransmit the driving force to the projectile.
 8. The sabot device ofclaim 7 wherein at least one of said longitudinal struts is inclinedwith respect to said arcuate outer surface.
 9. The sabot device to claim7 wherein at least two of said longitudinal struts are integrally formedalong the lateral edges of said petal segment forming a flat surfacewhereby the flat surfaces of abutting petal segments form planes ofseparation.
 10. The sabot device of claim 9 further comprising anadditional longitudinal strut positioned between said lateral edgestruts and inclined with respect to a perpendicular to said arcuateouter surface.
 11. The sabot device of claim 10 wherein said drive meanscomprise a plurality of driving band sections positioned within a recessin said petal segments.
 12. The sabot device of claim 11 wherein saidsecuring means comprise a holding band positioned in a second recess insaid petal segments adapted to rupture under centrifugal force.
 13. Thesabot device of claim 12 further comprising an annular wedge ringpositioned on the projectile forwardly of said petal segments and acontoured obturator abutting said inwardly curved end portion of saidpetal segments.
 14. In combination, a projectile having a plurality oflongitudinally extending grooves circumferentially spaced on theexterior, aft surface and a sabot device comprising: a plurality ofseparable petal segments, each segment having arcuate, longitudinallyextending inner and outer surfaces with an inwardly-curved, J-shaped,longitudinal end portion, and a plurality of longitudinal support strutsintegrally formed with and extending the longitudinal length of saidinner surface to engage said longitudinal grooves; projectile drivemeans positioned on said petal segments; and rupturable securing meansreceivable on said petal segments to hold said segments in assembledcondition on said projectile.
 15. The combination of claim 14 furthercomprising a circuMferential groove formed in the aft end portion ofsaid projectile to receive said inwardly curved, J-shaped end portion ofsaid petal segments.
 16. The combination of claim 15 wherein at leastone of said longitudinal struts is inclined with respect to the radialdirection of said arcuate surfaces.
 17. The combination of claim 16wherein said projectile drive means comprise sections of a driving bandpositioned within a recess in said petal segments and said rupturablesecuring means comprise a notched holding band.
 18. The combination ofclaim 17 further comprising: an annular wedge ring positioned on saidprojectile forwardly of said petal segments and an obturator positionedaft of said projectile abutting said petal segments.
 19. The combinationof claim 14 further comprising: an annular wedge ring positioned on saidprojectile forwardly of said petal segments and an obturator positionedaft of said projectile abutting said petal segments.